The High Dam, or el-Sadd el-Ali, some 4mi/7km above the old Aswan Dam, is a massive accumulation of 55.9 billion cu. yd/42.7 billion cu. m (17 times the volume of the Pyramid of Cheops) of stones and sand with a clay core and a concrete facing. With a total length of 2.5mi/3.6km, it pounds the waters of the Nile, which was originally 550yd/ 500m wide at this point.
It is no less than 1,070yds/ 980m thick at the base, reducing to 44yd /40m at the top. The top of the dam is 364ft/111m above the base and 643ft/196m above sea level. The average capacity of the reservoir (Lake Nasser) formed by the dam is some 177 billion cu. yds/135 billion cu. m, its maximum capacity 205 billion cu. yd/157 billion cu. m. Of this total quantity 110 billion cu. yd/84 billion cu. m the average annual flow of the Nile are assigned to irrigation, Egypt receiving 73 billion cu. yd/5.5 billion cu. m and Sudan 24 billion cu. yds/ 18.5 billion cu. m. It is estimated that over the next 500 years some 39 billion cu. yds/30 billion cu. m of capacity will be lost by the deposition of sediment; and some 8 billion cu. yd/6 billion cu. m of water are lost every year by evaporation. The remaining 48 billion cu. yd/37 billion cu. m of capacity are held in reserve against an unexpectedly high flow of water. A four lane road runs across the top of the dam. A memorial, a triumphal arch and an inscription commemorate the completion of this huge enterprise and the cooperation between Egypt and the Soviet Union in its realization.
It is not yet possible to assess completely the positive and negative effects of the High Dam. One undoubted benefit has been an increase of 20-30% (1,250,000-2,000,000 acres) in cultivated land, together with increased agricultural yields as a result of even and regular irrigation. Other clear gains are the increased output of electricity, the elimination of unpredictable floods and droughts, the possibility of navigation on the Nile throughout the year and the resources of food yielded by the fish of Lake Nasser. One negative result has been the loss of the fertilizing mud formerly deposited by the Nile, which now has to be made good by expensive artificial fertilizers; and consideration is now being given to the possibility of mechanical means of swirling the water in the reservoir in order to prevent it from depositing its alluvium there. Other disadvantageous effects have been the fall in the underground watertable in consequence of the faster and more direct flow of the river and the build up of salt in the soil, which is no longer washed out by regular flooding with fresh water. In order to obviate these side effects it will be necessary to construct further dams between Aswan and Cairo. The coastal regions of the Nile Delta have also suffered bythe loss of the fertile alluvium formerly carried down by the Nile; and the lack of natural foodstuffs in the water of the river has led to a considerable reduction in the stocks of fish in the south eastern Mediterranean. Another potential cause for concern is the possibility of damage to the High Dam by enemy action. The bursting of the dam would devastate the whole of Egypt and wipe out 98% of the population; and even the arrangements already provided to bring about a rapid fall in the level of Lake Nasser cannot eliminate the danger that would result from a surprise attack.